Recently, the development of word processing software and the spread of digital cameras facilitate importing an image in a document, and documents containing color images become popular. Digital copying machines and network copying machines have also advanced.
In this situation, electronic data of paper documents distributed at a meeting and the like can be managed in, e.g., a document management server. If necessary, electronic data managed in the document management server can be retrieved and subjected to various processes.
These processes include, for example, printing of retrieved electronic data, distribution to a terminal such as a desired personal computer (PC) within a network, save in a desired storage medium within a network, and editing.
One of retrieval methods of retrieving electronic data is to retrieve desired electronic data from the document management server by using text data contained in electronic data as a retrieval condition.
In Japanese Patent Laid-Open No. 2001-257862, when a paper document is to be converted into electronic data, an identification code is added to the electronic data to generate a printed material containing the identification code. To retrieve or print electronic data corresponding to the printed material, the printed material is loaded to recognize the identification code printed on the material, thereby retrieving or printing desired electronic data.
When a paper document to be distributed is created from original document data of color images, the purpose is reference/confirmation, and many copies must be formed. Thus, a paper document for such purpose is generally a paper document of grayscale images prepared by copying an original paper document by a copying machine or a paper document of monochrome images prepared by printing original document data by a monochrome printer.
In retrieving original document data from electronic data of a paper document containing a grayscale or monochrome image, when the original document data is formed by only text data, it can be accurately retrieved using the text data as a retrieval condition.
If, however, original document data contains a color image and is retrieved using text data as a retrieval condition, desired original document data cannot be retrieved or satisfactory precision cannot be obtained when the text data are identical but images are different.
In Japanese Patent Laid-Open No. 2001-257862, original document data needs to be printed once together with an identification code, and thus a change is inevitable for the original document data. A change not intended by the user is added to the original document data.
For example, to manage electronic data created by word processing software or the like as original document data, the electronic data is printed once, the printed material is loaded as electronic data, and then the electronic data is printed together with an identification code. Further, the printed material with the identification code is loaded as electronic data, resulting in cumbersome procedures.